We describe an instrument which measures the cross correlation between two vibration–rotation bands, over spectral regions containing 10 or more lines. A reference gas is contained in a pressure-modulated absorption cell, and the instrument responds selectively to the presence of this gas in an unknown mixture contained in a second absorption tube. The only fundamental limitation on the selectivity is imposed by errors in the multiplication property of band spectra.
Laboratory tests show that errors in determining the amount of nitrous oxide, from a band strongly overlapped by an ammonia band, are small.
Band parameters for the (200) band of nitrous oxide are obtained and used in a theoretical model of the instrument. Satisfactory agreement is obtained with laboratory calibrations. The model, with empirical corrections, is then applied to solar spectra, and the zenith amount of atmospheric nitrous oxide on two days is shown to be 0.24 atm-cm.
The performance of this system is compared with that of Strong’s Benedictine slits and a new system is proposed combining the advantages of both.
© 1968 Optical Society of AmericaFull Article | PDF Article
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